如何抓取开了gzip的网页

浏览数：34 / 时间：2015年06月09日

有时候用 file_get_contents() 函数抓取网页会发生乱码现象。有两个原因会导致乱码，一个是编码问题，一个是目标页面开了Gzip。

编码问题好办，把抓取到的内容转下编码即可($content=iconv("GBK", "UTF-8//IGNORE", $content);)，我们这里讨论的是如何抓取开了Gzip的页面。怎么判断呢？获取的头部当中有Content-Encoding: gzip说明内容是GZIP压缩的。用FireBug看一下就知道页面开了gzip没有。下面是用firebug查看我的博客的头信息，Gzip是开了的。繁峙县粮食局

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请求头信息原始头信息

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Accept  text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

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Accept-Encoding gzip, deflate

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Accept-Language zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3

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Connection  keep-alive

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Cookie  __utma=225240837.787252530.1317310581.1335406161.1335411401.1537; __utmz=225240837.1326850415.887.3.utmcsr=google|utmccn=(organic)|utmcmd=organic|utmctr=%E4%BB%BB%E4%BD%95%E9%A1%B9%E7%9B%AE%E9%83%BD%E4%B8%8D%E4%BC%9A%E9%82%A3%E4%B9%88%E7%AE%80%E5%8D%95%20site%3Awww.nowamagic.net; PHPSESSID=888mj4425p8s0m7s0frre3ovc7; __utmc=225240837; __utmb=225240837.1.10.1335411401

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Host    www.nowamagic.net

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User-Agent  Mozilla/5.0 (Windows NT 5.1; rv:12.0) Gecko/20100101 Firefox/12.0

下面介绍一些解决方案：

1. 使用自带的zlib库

如果服务器已经装了zlib库，用下面的代码可以轻易解决乱码问题。

`1`	`$data` `=` `file_get_contents("compress.zlib://".$url);`

2. 使用CURL代替file_get_contents

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function curl_get($url, $gzip=false){

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    $curl = curl_init($url);

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    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);

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    curl_setopt($curl, CURLOPT_CONNECTTIMEOUT, 10);

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    if($gzip) curl_setopt($curl, CURLOPT_ENCODING, "gzip"); // 关键在这里

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    $content = curl_exec($curl);

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    curl_close($curl);

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    return $content;

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}

3. 使用gzip解压函数

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function gzdecode($data) { 

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  $len = strlen($data); 

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  if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) { 

004
    return null;  // Not GZIP format (See RFC 1952) 

005
  } 

006
  $method = ord(substr($data,2,1));  // Compression method 

007
  $flags  = ord(substr($data,3,1));  // Flags 

008
  if ($flags & 31 != $flags) { 

009
    // Reserved bits are set -- NOT ALLOWED by RFC 1952 

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    return null; 

011
  } 

012
  // NOTE: $mtime may be negative (PHP integer limitations) 

013
  $mtime = unpack("V", substr($data,4,4)); 

014
  $mtime = $mtime[1]; 

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  $xfl   = substr($data,8,1); 

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  $os    = substr($data,8,1); 

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  $headerlen = 10; 

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  $extralen  = 0; 

019
  $extra     = ""; 

020
  if ($flags & 4) { 

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    // 2-byte length prefixed EXTRA data in header 

022
    if ($len - $headerlen - 2 < 8) { 

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      return false;    // Invalid format 

024
    } 

025
    $extralen = unpack("v",substr($data,8,2)); 

026
    $extralen = $extralen[1]; 

027
    if ($len - $headerlen - 2 - $extralen < 8) { 

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      return false;    // Invalid format 

029
    } 

030
    $extra = substr($data,10,$extralen); 

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    $headerlen += 2 + $extralen; 

032
  } 

033
 
034
  $filenamelen = 0; 

035
  $filename = ""; 

036
  if ($flags & 8) { 

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    // C-style string file NAME data in header 

038
    if ($len - $headerlen - 1 < 8) { 

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      return false;    // Invalid format 

040
    } 

041
    $filenamelen = strpos(substr($data,8+$extralen),chr(0)); 

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    if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) { 

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      return false;    // Invalid format 

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    } 

045
    $filename = substr($data,$headerlen,$filenamelen); 

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    $headerlen += $filenamelen + 1; 

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  } 

048
 
049
  $commentlen = 0; 

050
  $comment = ""; 

051
  if ($flags & 16) { 

052
    // C-style string COMMENT data in header 

053
    if ($len - $headerlen - 1 < 8) { 

054
      return false;    // Invalid format 

055
    } 

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    $commentlen = strpos(substr($data,8+$extralen+$filenamelen),chr(0)); 

057
    if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) { 

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      return false;    // Invalid header format 

059
    } 

060
    $comment = substr($data,$headerlen,$commentlen); 

061
    $headerlen += $commentlen + 1; 

062
  } 

063
 
064
  $headercrc = ""; 

065
  if ($flags & 1) { 

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    // 2-bytes (lowest order) of CRC32 on header present 

067
    if ($len - $headerlen - 2 < 8) { 

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      return false;    // Invalid format 

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    } 

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    $calccrc = crc32(substr($data,0,$headerlen)) & 0xffff; 

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    $headercrc = unpack("v", substr($data,$headerlen,2)); 

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    $headercrc = $headercrc[1]; 

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    if ($headercrc != $calccrc) { 

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      return false;    // Bad header CRC 

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    } 

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    $headerlen += 2; 

077
  } 

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  // GZIP FOOTER - These be negative due to PHP‘s limitations 

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  $datacrc = unpack("V",substr($data,-8,4)); 

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  $datacrc = $datacrc[1]; 

082
  $isize = unpack("V",substr($data,-4)); 

083
  $isize = $isize[1]; 

084
 
085
  // Perform the decompression: 

086
  $bodylen = $len-$headerlen-8; 

087
  if ($bodylen < 1) { 

088
    // This should never happen - IMPLEMENTATION BUG! 

089
    return null; 

090
  } 

091
  $body = substr($data,$headerlen,$bodylen); 

092
  $data = ""; 

093
  if ($bodylen > 0) { 

094
    switch ($method) { 

095
      case 8: 

096
        // Currently the only supported compression method: 

097
        $data = gzinflate($body); 

098
        break; 

099
      default: 

100
        // Unknown compression method 

101
        return false; 

102
    } 

103
  } else { 

104
    // I‘m not sure if zero-byte body content is allowed. 

105
    // Allow it for now...  Do nothing... 

106
  } 

107
 
108
  // Verifiy decompressed size and CRC32: 

109
  // NOTE: This may fail with large data sizes depending on how 

110
  //       PHP‘s integer limitations affect strlen() since $isize 

111
  //       may be negative for large sizes. 

112
  if ($isize != strlen($data) || crc32($data) != $datacrc) { 

113
    // Bad format!  Length or CRC doesn‘t match! 

114
    return false; 

115
  } 

116
  return $data; 

117
}